Well, to be fair, everything is a 'sitting duck' against this threat, especially as they get more and more advanced, with longer ranges and loitering times, specialized payloads and fully autonomous network-free AI capability. There is no effective counter against drone swarms yet.
Assuming that those drones are slow and hot would it be so hard to make a IR guided machine gun like a mini CIWS. Maybe it's enough to give current RWS new sensors and software.